ROCK Cooperated with ET-1 to Induce Epithelial to Mesenchymal Transition through SLUG in Human Ovarian Cancer Cells

The Rho-associated serine-threonine protein kinase (ROCK) is a downstream effector of Rho GTPases that is frequently activated in the epithelial to mesenchymal transition (EMT) of human ovarian cancer cells. On the other hand, endothelin-1 (ET-1) and its receptor endothelin A receptor (ET(A)R) are overexpressed in primary and metastatic ovarian carcinoma, which suggests that ET-1 promotes tumor dissemination. Hence, two human ovarian carcinoma cell lines, SK-OV-3 and CaOV3, were chosen to study the effects of ET-1/ET(A)R and ROCK in promoting EMT of ovarian cancer cells. We found that ET-1 exposure induced EMT of SK-OV-3 and CaOV3 by monitoring cells morphology, enhanced fibronectin, and reduced E-cadherin protein. At the same time, ET-1/ET(A)R enhanced the level of transcription of SLUG a transcriptional repressor of E-cadherin. More importantly, a constitutively active mutant of ROCK enhanced the transcription of SLUG by stimulating SLUG promoter activity. Furthermore, ROCK inhibitor Y27632 reversed the increase in fibronectin induced by ET-1/ET(A)R. Our data suggest that ROCK cooperated with ET-1/ET(A)R to promote EMT of human ovarian carcinoma cells through upregulation of SLUG mRNA.